How exactly does a capacitive digitizer work?
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A capacitive digitizer is a device that uses electrostatic charges to detect and locate touch. When an object, such as a finger, comes into contact with the surface of the digitizer, it disturbs the electrostatic field and the device can then determine the location of the touch.
By “capacitive digitizer”, do you mean the capacitive touch screen of a typical cell phone. There are several different methods for creating the sensing system. The typical one used on cell phones is a mutual capacitance projected capacitance method.
There is a grid of wires across the screen–usually not a whole lot maybe 10 to 20 in the x and y position. When your finger or other conductive object gets close to these wires it reduces the capacitance between the grid lines. The capacitance is measured at each grid location creating a low resolution capacitive “image”. Your finger is large enough to cover multiple nodes in the grid. Each of these nodes will have their capacitance reduced–the more your finger covers a node the greater the reduction in the capacitance. A controller is used to process this low resolution image and locate the estimated point of contact. The mutual capacitance method allows for multiple touches to be detected, whereas the other forms do not.
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